Winterize RV using a “Schrader valve”?

Dear Gary,
I have been hearing about dry winterizing a motorhome using a “Schrader valve” and blowing the water out using an air compressor set on 20-PSI, plus putting some of the pink stuff in the kitchen sink, bath sink and shower drains only. Is this a good idea? If so, how do I find the Schrader valve and where do I install one? —Bobbie V.

Dear Bobbie,
The device you are seeking that incorporates a Schrader valve is called a blowout plug. It has the air inlet valve (Schrader valve) on one end and a male hose fitting on the other end. Mine is made out of milled aluminum, but I’ve seen brass blowout plugs as well as inexpensive plastic blowout plugs. I do recommend the metallic type.

The blowout plug attaches directly to the city water inlet hose connection, but only temporarily; it isn’t a permanent installation. Clean compressed air is then forced into the system to expel the water through the faucets and low point drain locations. It’s the quickest way to rid the fresh water system of water. Professional shops use them all the time while performing winterizing procedures or when an RV is going to be stored for any length of time.

As you drain the fresh water tank and water heater, attach the blowout plug to the city water inlet. Open all faucets plus the hot and cold low level drain valves and then inject clean air. You can certainly apply more than 20-PSI since the entire piping system is pressure-tested at 80-PSI at the factory. And since all the faucets and valves will be open, it will be safe and quicker to use 80-PSI. Be sure it is clean air! Like I tell my seminar attendees, this is your fresh water system! Avoid using gas/filling station air or any air from a compressor equipped with a tank. The chance of contamination is greater if the compressor has a storage tank.

In addition, pour 1/4-cup of RV antifreeze down each drain to fill the P-traps, and you should be set for winter or any period of non-use.

You can purchase a blowout plug at any RV dealer or service center’s parts and accessories department and many websites online, including Amazon.

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I’ve found Schrader valves like the one shown sometimes do not pass enough volume of air to BLOW the water out so much as relieving the vacuum of what wants to flow out. When you remove the inadequate pressure, water may belly again in enough volume to freeze damage. I use a brass plug that connects directly to the compressor’s quick connect.

You don’t use 80psI because older pipes can’t take it, and its more abuse than needed. 30-40psi is what most shops use.

You pretty much NEED to use a tanked compressor to generate enough airflow! Contamination is a mild concern with ANY compressor, but inline air filters are CHEAP. I’ve yet to hear any issues from people who didn’t bother with the filter, but my compressor runs through a filter all the time anyway – dry clean air is better for my tools.

Thanks for the detailed info, Gary, on winterizing. However, the Owners Manual for my 2005 Itasca Cambria (Winnebago) says not to use more than 30 psi to blow out the system, and it seems like you’re saying 80 psi is commonly used. I guess if the shops are winterizing with that psi and nothing bad has happened yet, it must be okay, but a recommended difference of 50 psi seems odd.

In your article about compressed air to blow out water lines. you mention not to use air from a compressor with a tank. Why not if you keep the tank drained and clean them it is good to go. I have been using it that way for the last 15 years on three different units and have had no problems.

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